From 1838 to 1856, he was the first President of the Ballston Spa Bank (later Ballston Spa National Bank) and also was the owner of cotton mills at Ballston Spa.
At the state election in November 1851, he was elected New York State Treasurer on the Whig ticket by a margin of only 228 votes (200,693 for Cook; 200,465 for Welch), and took office on January 1, 1852. His Democratic opponent Benjamin Welch, Jr. contested the election successfully, and on November 20, 1852, Welch succeeded to the office for the remainder of the term.